﻿/* Copyright 2010-present MongoDB Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

using MongoDB.Driver.Linq.Linq3Implementation.Ast.Expressions;
using MongoDB.Driver.Linq.Linq3Implementation.Ast.Stages;

namespace MongoDB.Driver.Linq.Linq3Implementation.Ast.Optimizers
{
    internal class AstFindProjectionSimplifier : AstSimplifier
    {
        public override AstNode VisitProjectStageSetFieldSpecification(AstProjectStageSetFieldSpecification node)
        {
            node = (AstProjectStageSetFieldSpecification)base.VisitProjectStageSetFieldSpecification(node);

            // { path : '$path' } => { path : 1 }
            if (node.Value is AstFieldPathExpression fieldPathExpression &&
                fieldPathExpression.Path == $"${node.Path}")
            {
                return AstProject.Include(node.Path);
            }

            return node;
        }
    }
}
